Lorena Rebolledo - Academia.edu (original) (raw)

Papers by Lorena Rebolledo

Antarctic Science

The changes implemented in 2005 in the development strategies of Antarctic science carried out by... more The changes implemented in 2005 in the development strategies of Antarctic science carried out by Chile have had a positive impact on the scientific productivity of the Chilean Antarctic Science Program (PROCIEN). We analysed scientometric indicators from between 2009 and 2019. The bibliographic data were extracted from the Web of Science database using search query keywords. We used multiple correspondence analysis to identify specific trends and also network analyses of international collaboration in VOSviewer. The number of Antarctic science publications in Chile has gradually increased from 21 in 2009 to 95 in 2019. The rise in the number of articles was higher in journals for the first impact factor quartile. Research lines showing increased first-quartile impact factor papers corresponded to Antarctic ecosystems, biotechnology and geosciences. The main geographical domains in which such research activities have been carried out corresponded to in the South Shetland Islands and...

Fjord ecosystems are located in high latitude environments across Scandinavia, Alaska, Canada, Ch... more Fjord ecosystems are located in high latitude environments across Scandinavia, Alaska, Canada, Chile, New Zealand, and some more northerly Antarctic and Arctic environments (Freeland et al. 1980). Fjords are water bodies with variable-depth estuarine features, are highly stratified, and are influenced by tidal currents (Pickard 1961; Wassmann et al. 2000). One of the largest regions of fjords in the world is the Chilean Patagonia (from 41º to 56ºS), stretching over 241,000 Km2 with islands, channels, estuaries, bays and gulfs formed by glacial erosion over the current quaternary (Borgel 1970; Holtedahl 2006; Aracena et al. 2015). This fjord region is characterized by low concentrations of dissolved inorganic nutrients in surface waters, and high concentrations of nutrients supplied by sub-Antarctic ocean waters (Silva et al. 1997, 1998; Silva 2008; González et al. 2011). Stratification in the water column is a barrier that reduces the export of phytoplanktonic carbon and influences the distribution of some zooplankton groups (Ji et al. 2010; González et al. 2011; Tamelander et al. 2012). Fjords are important sites for carbon cycles and biological productivity (Wetzel 2001; González et al. 2006; Pomeroy 2006), and are sensitive to environmental and climatic changes (Overpeck et al. 1997; Svendsen et al. 2002; Whitehead et al. 2009).

This study aims at establishing past variations of the main oceanographic and climatic features i... more This study aims at establishing past variations of the main oceanographic and climatic features in the Central Chilean coast, using recent sedimentary records of a transitional semi-arid ecosystem susceptible to environmental forcing conditions. Coquimbo (30°S) region is characterized by dry summers and short rainfall periods during winter. The relatively wet-winter climate results from the interactions between the southern westerly winds and the South Pacific Anticyclone (SPA); in summer, the SPA moves southwards while in winter it returns to the north, allowing the passage of storm fronts. This semiarid zone is strongly affected by variations associated with El Niño-Southern Oscillation (ENSO), caused by seasonal latitudinal changes in the SPA that produce high variability and precipitation in Chilean mid-latitudes. Sediment cores were retrieved in two bays, Guanaqueros and Tongoy, for geochemical analyses including: sensitive redox trace elements, biogenic opal, total organic carbon (TOC), diatoms, stable isotopes of organic carbon and nitrogen. The results suggest a main dry phase of high primary productivity concomitant with high fluxes of organic compounds to the bottom and suboxic-anoxic conditions in the sediments. This period reached a maximum at cal BC ~4500, followed by a continuous increase in wet conditions, low primary productivity and a more oxygenated environment towards the present, being remarkably stronger in the last 2000 years. We suggest that this might be associated with greater El Niño frequencies or similar conditions that increase precipitation, concomitantly with the introduction of oxygenated waters to coastal zones by the propagation of equatorial origin waves.

Biogeosciences, Nov 24, 2020

The aim of this project was to establish past variations in the main oceanographic and climatic f... more The aim of this project was to establish past variations in the main oceanographic and climatic features of a transitional semiarid ecosystem on the north-central Chilean coast. We analyzed recent sedimentary records retrieved from two bays, Guanaqueros and Tongoy (30 • S), for geochemical and biological analyses, including the following: sensitive redox trace elements, biogenic opal, total organic carbon (TOC), diatoms and stable isotopes of organic carbon and nitrogen. Three remarkable periods were established with different environmental conditions and productivities: (1) > 6600 cal BP, (2) 4500-1800 cal BP and (3) 140 cal BP to the present (2015 CE). The first period was characterized by a remarkably higher productivity (higher diatom abundances and opal) in which large fluxes of organic compounds were also inferred from the accumulation of elements, such as Ba, Ca, Ni, Cd and P, in the sediments. Meanwhile, significantly reduced conditions at the bottom of the bays were suggested based on the large accumulation of Mo, Re and U, showing a peak at 6600 cal BP, when sulfidic conditions could have been present. According to the pollen moisture index (PMI), this was also identified as the driest interval. These conditions should be associated with an intensification of the Southern Pacific Subtropical Anticyclone (SPSA) and stronger southerly western winds, emulating La Niñalike conditions, as has been described for the SE Pacific during the early Holocene and part of the mid-Holocene. During most of the second period, lower productivity was observed; however, a small increase was identified between 3400 and 4000 cal BP, although lower amounts of diatom (valves g −1) and nutrient-type metal accumulations were evident. Anoxic Published by Copernicus Publications on behalf of the European Geosciences Union. 5764 P. Muñoz et al.: Reconstructing past variations in environmental conditions conditions at the bottom of the bays changed to an almost stable suboxic condition during this time interval. The third period was marked by intense oxygenation after 1800 cal BP, as observed by a drastic change in the accumulation of U, Mo and Re. This was followed by a return to more reduced conditions over the past 2 centuries, characterized by a small productivity rise after ∼ 140 cal BP, as suggested by the opal accumulations. Overall, lower primary productivity, lower reduced conditions at the bottom and higher-humidity conditions were established after 6600 cal BP to the present. We suggest that the oxygenation might be associated with a weak effect from the oxygen minimum zone over the shelf and intensified El Niño activity, introducing oxygenated waters to the coastal zones through the propagation of equatorial waves and establishment of conditions that reduced the primary productivity from the mid-Holocene toward the beginning of the modern era.

DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2005

Global and Planetary Change, Oct 1, 2021

Abstract With a growing concern over rapid Antarctic ice loss in recent years, the Amundsen Sea, ... more Abstract With a growing concern over rapid Antarctic ice loss in recent years, the Amundsen Sea, one of the fastest-melting areas in Antarctica, currently becomes a hotspot for the Earth sciences in the context of its linkage to global climate. As a center of strong physical and biological coupling processes, polynyas of the Amundsen Sea could act as sentinels of changes in atmosphere–ice–ocean interactions, offering a unique perspective into its sensitivity to climate variability. Here, we present a new, multiproxy-based high-resolution sedimentary record from the Amundsen Sea polynya, which provides new insights into environmental conditions of the region over the last 350 years and their linkages to climatic factors. Our results show that the polynya witnessed step-wise environmental shifts in parallel with the phases and strength of large-scale climate patterns, i.e., the Southern Annular Mode (SAM) and El Nino-Southern Oscillation (ENSO). Notably, intersite correlation of on-shelf Circumpolar Deep Water (CDW) intrusion signals at different locals suggests that the CDW may have gained increased access to the shelves at the time of a strong coupling of positive SAM and El Nino states. We tentatively speculate that anomalous large-scale atmospheric and oceanic circulation patterns over the Southern Hemisphere, forced by increasing greenhouse gas levels, were strongly involved in the mid-20th century CDW invigoration, which may be greater in scale that goes well beyond the Amundsen Sea region. This result is relevant to the current debate on spatial heterogeneity in the timing and phasing of major climatic events in Antarctica, underscoring an unambiguous connection of the Antarctic climate state to the large-scale ocean-atmosphere reorganizations. Our study also extends a growing evidence that today's global warming trend is expected to have a severe effect on future configuration of Antarctic continental ice-shelf environment.

Polar Biology, 2021

The study of fatty acid biomarkers in trophic structures at sub-polar latitudes is fundamental in... more The study of fatty acid biomarkers in trophic structures at sub-polar latitudes is fundamental in describing energy fluxes across ecosystems characterized by complex inter-specific interactions. Due to the presence of certain essential fatty acids obtained exclusively from predator–prey interactions, fatty acid biomarkers are widely used to identify trophic interactions. This study analyzed fatty acid compositions in three species inhabiting a relatively pristine Patagonian fjord. This fjord is geographically difficult to access, so there are very little sampling opportunities, biological and oceanographic information. In the three species collected ( Ctenodiscus australis (Loven in Lütken 1871) (Echinodermata, Asteroidea, Ctenodiscidae); Munida gregaria (Fabricius 1793) (Arthropoda, Malacostraca, Munididae); Eleginops maclovinus (Cuvier 1830) (Chordata, Actinopterygii, Eleginopsidae)) along this remote area were evaluated their fatty acid trophic markers as a tool to differentiate dietary components and dietary habits. The study reported significant differences in the amount of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA), with the highest concentrations of all fatty acids in M. gregaria . The last suggests that M. gregaria is considered as a good quality food source or biological component that might support the fjord trophic web in the Southern Hemisphere. The results describe diet compositions in sampled species, and differences among species for fatty acid compositions and proportions. This provides an initial basis for future modeling or projecting how benthic ecosystems of fjords and Patagonian channels respond to food intake, particularly in environments associated with glacial systems characterized by a low phytoplankton biomass and greater sensitivity to climate variability.

Canadian Journal of Fisheries and Aquatic Sciences

Detailed knowledge of marine mammal diet is critical to understand their ecological roles and for... more Detailed knowledge of marine mammal diet is critical to understand their ecological roles and for the adequate management of marine resources. Antarctic fur seals ( Arctocephalus gazella) in the Southern Atlantic Ocean rely largely on Antarctic krill ( Euphausia superba) during the summer months, but their winter diet remains largely unknown. Here, stable carbon and nitrogen isotope ratios in whiskers and blood of young (2–3 years old) and subadult (4–7 years old) Antarctic fur seal males from the South Shetland Islands were used to assess the seasonal and interannual changes in the krill contribution to their diet. The stable isotope ratios revealed that krill dominated the diet of young and subadult male Antarctic fur seals year-round, with penguins, and not fish, as the second major prey, regardless of year and season. The year-round reliance of young and subadult male Antarctic fur seals on krill should be considered for ecosystem-based fisheries management, as they represent th...

DOAJ: Directory of Open Access Journals - DOAJ, Sep 1, 2005

Marine Ecology Progress Series, 2016

Complex marine−terrestrial interactions characterize Chilean fjords, where benthic communities in... more Complex marine−terrestrial interactions characterize Chilean fjords, where benthic communities influence the distribution of organic matter (OM). We examined spatial and seasonal changes in the hydrography, sediment conditions and soft-bottom macrobenthic, meiobenthic, and total microbial biomass in a glacial Patagonian fjord (Martinez Channel, Chile). The transport of a high load of glacial mineral and particulate OM to the fjord in the austral summer coincided with low total live benthic biomass. Multivariate analysis evidenced temporal-related macrofaunal groups influenced by the different environments produced by the advection of sediment transport and terrestrial OM from the Baker River, Chile. The relationships between density/biomass and respiration versus body size varied considerably with distance from major riverine inputs, but the slopes of density size spectra and normalized biomass size spectra were less negative in summer than in winter. Occasional large-scale advective processes in the water column affected sediment conditions and removed surface macrofauna, influencing the slope and intercept of the regression models. In the outer fjord, lateral advection and subsequent sedimentation of terrestrial OM contributed a significant fraction to total OM sediments (<14.76%). Stable carbon isotopes measured in benthic organisms suggest that benthic communities in the inner fjord may assimilate a significant fraction of terrestrial OM via heterotrophic bacteria in contrast to the minor input of terrestrial OM in the outer fjord.

ABSTRACT Although metropolitan central Chile (32-35oS) has a 470-year-long written seismic histor... more ABSTRACT Although metropolitan central Chile (32-35oS) has a 470-year-long written seismic history, the country’s longest, no attempt has been made to match this history with the geological record. Doing so would extend back in time, perhaps in thousands of years, the seismic story of the Chile’s most populated area. Here, we use historical, sedimentary and biological evidence to reconstruct the paleoseismic record of central Chile. A coastal lowland site north of Valparaíso contains geological and biological evidence for three instances of coseismic uplift, with accompanying paleotsunami deposits. Each earthquake is marked by a buried soil sharply overlain by a distinct, tabular, and laterally continuous sheet of pale sand. The inferred earthquakes and tsunami deposits are dated to 4,300, 3,800, 3,500 yrs BP from in situ plant remains. This record of paleoseismicity in central Chile is typical of a subduction zone coastline that has experienced falling relative sea-levels during the late Holocene. During the early to mid-Holocene, regional sea-level rise that culminates in a highstand creates the accommodation space necessary for the preservation of such coastal stratigraphy. Analysis of the particle size and lithology indicate a strong similarity between the inferred paleotsunami deposits, which consist mainly of fine sand (150-225 mm) with micaceous particles, and modern beach and surf sand (175-225 mm). Samples collected from old dunes that surround the study area are composed of medium (>275 mm) reddish-tan sand, with no mica, ruling out aeolian deposition of the sand-sheets. Normal grading, which is characteristic of sediment settling out of suspension and is often observed in modern tsunami deposits, is present in two of the three sands. Fossil diatom assemblages vertically spanning each buried soil also provide paleoecological evidence to support the oceanward source of the sand deposits and reveal evidence of coseismic uplift. Buried soils are dominated by low-marsh brackish species while overlying sands are composed of a mixture of marine species common on tidal flats, marine spores, low-marsh brackish species, and high-marsh freshwater species. Soils overlying each sand deposit display a clear paleoecological shift to fresher high-marsh taxa, indicating sudden and lasting coseismic uplift.